New Features: Toggling shape visibility on right click; Support constrained shape rotating

[lyxok1]

Feature 1: Support shape visibility toggling on right click menu

Motivation: allowing quickly show/hide annotation shapes on right click; instead of frequently moving to the View menu and toggling it.

• a video example

toggle.mp4

Feature 2: Support shape rotation

Motivation: allowing shape rotation aound its center point as original

• Support rotating the selected shapes by pressing key R and then moving the mouse up and down

• Render the rotation center of each shape during adjustment of rotation

• Block the hovering or highlighting behavior when some shapes are being rotated

• Constrain the rotation when the rotated shapes go out of the pixelmap

• Get out the rotation mode and go back to normal edit mode by press key esc or key R again

• a video example

rotate.mp4